Earth formations may be used for various purposes such as hydrocarbon production, geothermal production, and carbon dioxide sequestration. In order to efficiently use an earth formation, the formation is characterized by performing measurements of many different properties using one or more tools conveyed through a borehole penetrating the formation. One category of tools is acoustic tools that use sound waves to perform various measurements such as measuring fluid impedance or fluid velocity of a fluid disposed in a borehole. One challenge presented by such tools is signal leakage, which can lower signal to noise ratio. Another challenge is signal interference caused by reflections of the signal leakage, which can distort the received signal. Hence, it would be well received in the drilling industry if acoustic downhole tools were developed that reduced acoustic signal leakage and acoustic signal reflections.